In recent years, a smaller size and a smaller thickness have been demanded for electric equipment such as portable information equipment. Accordingly, a higher package density has been required for electronic circuits. As means for increasing a density of an electronic circuit, instead of conventional IC packages, the field of flip-chip packaging method has remarkably developed, in which a semiconductor bare chip having a wafer divided into pieces is reversed upside down and is directly mounted on a circuit board. For example, packaging and modules currently produced by the flip-chip packaging method include CSP (Chip Size Package) in which packaging is made in the same size as a semiconductor bare chip and MCM (Multi Chip Module) in which a plurality of semiconductor bare chips are mounted on a circuit board. The production of these methods has increased. In SBB (Stud Bump Bonding) which is one of the flip-chip packaging methods, wire bonding method is applied to form bumps on electrode pads of a semiconductor bare chip and leveling is performed by a leveling device for leveling the bump heads of the bumps, so that stud bumps of two-stepped protrusions are formed, each having a bump base and a bump head.
Further, in recent years, techniques have been developed for mounting semiconductor bare chips on both surfaces of a circuit board by flip-chip method. FIGS. 5A to 5G are longitudinal sectional views showing a conventional manufacturing process of a semiconductor bare chip mounted module in the order of steps. The semiconductor bare chip mounted module has semiconductor bare chips mounted on both surfaces of a circuit board by flip-chip method. First, as shown in FIG. 5A, a thermosetting adhesive 3 made of epoxy is applied to board electrodes 2 on a first mounting surface 1a of a circuit board 1. The board electrodes 2 are formed on predetermined positions of circuits on both surfaces of the circuit board 1.
Meanwhile, as shown in FIG. 5B, on a semiconductor bare chip 4 to be mounted, stud bumps 8 (protruding electrodes) of two-stepped protrusions are formed on electrode pads 7 provided on one surface of the semiconductor bare chip 4. The stud bump 8 has a bump base 8a which is fused with the material of the electrode pad 7 so as to be firmly fixed as an alloy on the electrode pad 7 and a bump head 8b which is formed on the bump base 8a. The semiconductor bare chip 4 is sucked and held by a vacuum suction head 9 and is conveyed over the circuit board 1, and then, the semiconductor bare chip 4 is lightly pressed onto the thermosetting adhesive 3 and is temporarily fixed in a state that the stud bumps 8 are aligned with the board electrodes 2.
The circuit board 1 having the semiconductor bare chip 4 is temporarily fixed is conveyed to the subsequent step after the vacuum suction head 9 is separated. In the subsequent step, as shown in FIG. 5C, a pressure-heating head 10 is pressed and heated onto the temporarily fixed semiconductor bare chip 4 for about thirty seconds. Thus, as shown in FIG. 5D, the thermosetting adhesive 3 is thermally set and contracted, the contraction force permits the semiconductor bare chip 4 to be entirely attracted to the first mounting surface 1a of the circuit board 1, and the bump heads 8b of the stud bumps 8 are press-bonded and electrically connected to the corresponding board electrodes 2. Moreover, the semiconductor bare chip 4 is firmly bonded to the first mounting surface 1a via the adhesive 3 which is filled entirely into a gap between the semiconductor bare chip 4 and the first mounting surface 1a of the circuit board 1. In this way, mounting of the semiconductor bare chip 4 onto the first mounting surface 1a of the circuit board 1 is completed.
Subsequently, as shown in FIG. 5D, after the circuit board 1 is reversed upside down and the thermosetting adhesive 3 is applied to a second mounting surface 1b of the circuit board 1, the same mounting process as that of the first mounting surface 1a is performed. Namely, as shown in FIG. 5E, another semiconductor bare chip 4 which is sucked and held by the vacuum suction head 9 is pressed onto the thermosetting adhesive 3 and is temporarily fixed. Next, as shown in FIG. 5F, the pressure-heating head 10 is pressed onto the temporarily fixed semiconductor bare chip 4 for about thirty seconds in a heating state. Hence, as shown in FIG. 5G, the semiconductor bare chip 4 is mounted on the second mounting surface 1b via the thermosetting adhesive 3, and a semiconductor bare chip mounted module 12 is completed in which the semiconductor bare chips 4 are flip-chip mounted on the surfaces 1a and 1b of the circuit board 1.
However, in the above conventional method for manufacturing the semiconductor bare chip mounted module 12, as illustrated in FIG. 5D in an exaggerated manner, the circuit board 1 is deformed in a warping direction to the second mounting surface 1b due to the contraction force of a thermosetting resin after adhesive in the thermosetting adhesive 3 is cured on the first mounting surface 1a. For this reason, when the deformed circuit board 1 is reversed upside down and the semiconductor bare chip 4 is mounted on the second mounting surface 1b by using the pressure-heating head 10, stress is applied to the joints between the board electrodes 2 on the circuit board 1 and the stud bumps 8 of the semiconductor bare chip 4 mounted on the first mounting surface 1a, resulting in problems such as degradation in quality of the joints and bonding defects. Further, when the semiconductor bare chip 4 is mounted on the second mounting surface 1b, in the case where a relatively large warp occurs on the circuit board 1, a serious problem may arise that electrical connection cannot be made between the stud bumps 8 and the board electrodes 2 due to a displacement of the semiconductor bare chip 4, resulting in lower yields.
The present invention is devised in view of the above conventional problem and has as its objective the provision of a method for manufacturing a semiconductor device whereby semiconductor elements such as semiconductor bare chips can be mounted with high productivity on both surfaces of a circuit board in such a manner as to prevent a warp on the circuit board, and an apparatus for manufacturing a semiconductor device whereby the manufacturing method can be faithfully embodied.